Search

Background: There is a need to investigate mechanisms of phenotypic plasticity in marine invertebrates as negative effects of climate change, like ocean acidification, are experienced by coastal ecosystems. Environmentally-induced changes to the methylome may regulate gene expression, but methylome responses can be species- and tissue-specific. Tissue-specificity has implications for gonad tissue, as gonad-specific methylation patterns may be inherited by offspring. We used the Pacific oyster (Crassostrea gigas) — a model for understanding pH impacts on bivalve molecular physiology due to its genomic resources and importance in global aquaculture— to assess how low pH could impact the gonad methylome. Oysters were exposed to either low pH (7.31 ± 0.02) or ambient pH (7.82 ± 0.02) conditions for 7 weeks. Whole genome bisulfite sequencing was used to identify methylated regions in female oyster gonad samples. C- > T single nucleotide polymorphisms were identified and removed to ensure accurate methylation characterization. Results: Analysis of gonad methylomes revealed a total of 1284 differentially methylated loci (DML) found primarily in genes, with several genes containing multiple DML. Gene ontologies for genes containing DML were involved in development and stress response, suggesting methylation may promote gonad growth homeostasis in low pH conditions. Additionally, several of these genes were associated with cytoskeletal structure regulation, metabolism, and protein ubiquitination — commonly-observed responses to ocean acidification. Comparison of these DML with other Crassostrea spp. exposed to ocean acidification demonstrates that similar pathways, but not identical genes, are impacted by methylation. Conclusions: Our work suggests DNA methylation may have a regulatory role in gonad and larval development, which would shape adult and offspring responses to low pH stress. Combined with existing molluscan methylome research, our work further supports the need for tissue- and species-specific studies to understand the potential regulatory role of DNA methylation. [ABSTRACT FROM AUTHOR]

Abstract: Several bone conditions, eg, bone cancer, osteoporosis, and rheumatoid arthritis (RA), are associated with a risk of developing persistent pain. Increased osteoclast activity is often the hallmark of these bony pathologies and not only leads to bone remodeling but is also a source of pronociceptive factors that sensitize the bone-innervating nociceptors. Although historically bone loss in RA has been believed to be a consequence of inflammation, both bone erosion and pain can occur years before the symptom onset. Here, we have addressed the disconnection between inflammation, pain, and bone erosion by using a combination of 2 monoclonal antibodies isolated from B cells of patients with RA. We have found that mice injected with B02/B09 monoclonal antibodies (mAbs) developed a long-lasting mechanical hypersensitivity that was accompanied by bone erosion in the absence of joint edema or synovitis. Intriguingly, we have noted a lack of analgesic effect of naproxen and a moderate elevation of few inflammatory factors in the ankle joints suggesting that B02/B09-induced pain-like behavior does not depend on inflammatory processes. By contrast, we found that inhibiting osteoclast activity and acid-sensing ion channel 3 signaling prevented the development of B02/B09-mediated mechanical hypersensitivity. Moreover, we have identified secretory phospholipase A2 and lysophosphatidylcholine 16:0 as critical components of B02/B09-induced pain-like behavior and shown that treatment with a secretory phospholipase A2 inhibitor reversed B02/B09-induced mechanical hypersensitivity and bone erosion. Taken together, our study suggests a potential link between bone erosion and pain in a state of subclinical inflammation and offers a step forward in understanding the mechanisms of bone pain in diseases such as RA. [ABSTRACT FROM AUTHOR]

A number of studies confirmed the involvement of transient receptor potential vanilloid (TRPV) and acid-sensing (ASIC) ion channels in the physiological processes associated with the development of anxiety disorders. This makes their ligands new potential anxiolytic agents. We examined the efficacy of two peptides from the sea anemone Heteractis crispa, Hcr 1b-2 and HCRG21, affecting ASIC1a and TRPV1 channels, respectively, in the open field and elevated plus maze tests. According to the obtained data, HCRG21 significantly decreases both the level of anxiety and stimulates the activity of animals at doses of 0.01–1 mg/kg, whereas Hcr 1b-2 has a weak anxiolytic effect only at a dose of 0.1 mg/kg. The pharmacodynamic study showed that the HCRG21 has an anxiolytic effect for 2 h, and its effectiveness is higher than that of the reference drug. [ABSTRACT FROM AUTHOR]

A novel randomly branched polycation with good proton-buffering capability over a wide pH range (named PTEG) and its polyplexes with DNA were prepared and characterized by various techniques. Characterization via 1H NMR, 13C NMR, FTIR, TGA, DSC, element analysis and protonation titration showed the structure and physical, chemical properties of PTEG. Characterization via electrophoresis, dynamic light scattering, zeta potential analysis and AFM showed that PTEG and DNA formed colloidal complexes. The reason of strong proton-buffering capability below pH 7.4 (that is, proton sponge effect) of PTEG was deeply studied and the results showed that it had no relation with amino group kind. The real reason was series-wound coupled amino groups connected by two carbons, which provides a basis for the synthesis of cationic polymers with strong proton sponge effect. [ABSTRACT FROM AUTHOR]

Contrary to the long-standing opinion of boronic acids being typically reactive with 1,2- and 1,3-diols and hence not suitable for quantitative sensing of DNA containing only a mono-ol unit, this proof-of-concept study has successfully shown the feasibility to quantitatively detect DNA in the concentration range of 5 to 50 nM plausibly through boronic acid-mediated bridging of two DNA double helices via the 3′ hydroxy groups, which opens up new avenues in the realm of oligonucleotide biochemistry. [ABSTRACT FROM AUTHOR]

Ocean acidification is impacting marine life all over the world. Understanding how species can cope with the changes in seawater carbonate chemistry represents a challenging issue. We addressed this topic using underwater CO2 vents that naturally acidify some marine areas off the island of Ischia. In the most acidified area of the vents, having a mean pH value of 6.7, comparable to far‐future predicted acidification scenarios (by 2300), the biomass is dominated by the brown alga Sargassum vulgare. The novelty of the present study is the characterization of the S. vulgare proteome together with metabolite analyses to identify the key proteins, metabolites, and pathways affected by ocean acidification. A total of 367 and 387 proteins were identified in populations grown at pH that approximates the current global average (8.1) and acidified sites, respectively. Analysis of their relative abundance revealed that 304 proteins are present in samples from both sites: 111 proteins are either higher or exclusively present under acidified conditions, whereas 120 proteins are either lower or present only under control conditions. Functionally, under acidification, a decrease in proteins related to translation and post‐translational processes and an increase of proteins involved in photosynthesis, glycolysis, oxidation–reduction processes, and protein folding were observed. In addition, small‐molecule metabolism was affected, leading to a decrease of some fatty acids and antioxidant compounds under acidification. Overall, the results obtained by proteins and metabolites analyses, integrated with previous transcriptomic, physiological, and biochemical studies, allowed us to delineate the molecular strategies adopted by S. vulgare to grow in future acidified environments, including an increase of proteins involved in energetic metabolism, oxidation–reduction processes, and protein folding at the expense of proteins involved in translation and post‐translational processes. [ABSTRACT FROM AUTHOR]

Transcranial ultrasound stimulation is an emerging technique for the development of a non-invasive neuromodulation device for the treatment of various types of neurodegenerations and brain damages. However, there are very few studies that have quantified the optimal ultrasound dosage and the long-term associated effects of transcranial ultrasound treatments of brain diseases. In this study, we used a simple ex vivo hippocampal tissues stimulated by different dosages of ultrasound in combination with different chemical treatments to quantify the required energy for a measurable effect. After determining the most desirable ex vivo stimulation conditions, it was then replicated for the in vivo mouse brains. It was discovered that transcranial ultrasound promoted the increase of Tbr2-expressing neural progenitors in an ASIC1a-dependent manner. Furthermore, such effect was observable at least a week after the initial ultrasound treatments and was not abolished by auditory toxicity. • Minimal ultrasound energy required for in vitro hippocampus activation. • Ultrasound promotes the increase of Tbr2 positive progenitor in subgranular zone of dentate gyrus. • Ultrasound stimulates the p-ERK in trigeminal ganglia in ASIC3 dependent manner. • Ultrasound stimulation of p-ERK in mouse brain cannot be abolished by auditory toxicity. [ABSTRACT FROM AUTHOR]

Acid-sensing ion channels (ASICs) are neuronal, proton-gated, Na+-selective ion channels. They are involved in various physiological and pathological processes such as neurodegeneration after stroke, pain sensation, fear behavior and learning. To obtain information on the activation mechanism of ASIC1a, we attempted in this study to impose distance constraints between paired residues in different channel domains by using cross-linkers reacting with engineered Cys residues, and we measured how this affected channel function. First, the optical tweezer 4′-Bis(maleimido)azobenzene (BMA) was used, whose conformation changes depending on the wavelength of applied light. After exposure of channel mutants to BMA, an activation of the channel by light was only observed with a mutant containing a Cys mutation in the extracellular pore entry, I428C. Western blot analysis indicated that BMA did not cross-link Cys428 residues. Extracellular application of methanethiosulfonate (MTS) cross-linkers of different lengths changed the properties of several Cys mutants, in many cases likely without cross-linking two Cys residues. Our observations suggest that intersubunit cross-linking occurred in the wrist mutant A425C and intrasubunit cross-linking in the acidic pocket mutant D237C/I312C. In these mutants, exposure to cross-linkers favored a non-conducting channel conformation and induced an acidic shift of the pH dependence and a decrease of the maximal current amplitude. Overall, the cross-linking approaches appeared to be inefficient, possibly due to the geometrical requirements for successful reactions of the two ends of the cross-linking compound. [ABSTRACT FROM AUTHOR]

It is acknowledged that chronic inflammation is associated with a rise in extracellular proton concentrations. The acid-sensing ion channel 1a (ASIC1a) belongs to the extracellular H+- activated cation channel family. Recently, many studies have been conducted on ASIC1a and inflammatory immune diseases. Here, in this review, we will focus on the role of ASIC1a in several inflammatory immune diseases so as to provide new perspectives for clinical treatment. [ABSTRACT FROM AUTHOR]

FMRFamide (Phe-Met-Arg-Phe-amide, FMRFa) and similar neuropeptides are important physiological modulators in most invertebrates, but the molecular basis of FMRFa activity at its receptors is unknown. We therefore sought to identify the molecular determinants of FMRFa potency against one of its native targets, the excitatory FMRFa-gated sodium channel (FaNaC) from gastropod mollusks. Using molecular phylogenetics and electrophysiological measurement of neuropeptide activity, we identified a broad FaNaC family that includes mollusk and annelid channels gated by FMRFa, FVRIamides, and/or Wamides (or myoinhibitory peptides). A comparative analysis of this broader FaNaC family and other channels from the overarching degenerin (DEG)/epithelial sodium channel (ENaC) superfamily, incorporating mutagenesis and experimental dissection of channel function, identified a pocket of amino acid residues that determines activation of FaNaCs by neuropeptides. Although this pocket has diverged in distantly related DEG/ENaC channels that are activated by other ligands but enhanced by FMRFa, such as mammalian acid-sensing ion channels, we show that it nonetheless contains residues that determine enhancement of those channels by similar peptides. This study thus identifies amino acid residues that determine FMRFa neuropeptide activity at FaNaC receptor channels and illuminates the evolution of ligand recognition in one branch of the DEG/ENaC superfamily of ion channels. [ABSTRACT FROM AUTHOR]

The hybrid materials have great significance in gas detection, photocatalysis and humidity sensing. In this paper, the SnO2/SnO material was successfully obtained by annealing Sn6O4(OH)4 at 350°C. The Sn6O4(OH)4 sample was synthesized by the coprecipitation method. The XRD analysis confirmed the formation of SnO2 and SnO phases and XPS analysis validated the results of XRD analysis (presence of the Sn2+ and Sn4+ states). The N2 adsorption-desorption isotherm revealed the mesoporous characteristic of the material along with 41.386 m² g−1 BET surface area and 3.794 nm average pore diameter. As a sensing application, a sensor based on SnO2/SnO material was fabricated on the interdigitated electrodes and investigated under combined atmospheres of humidity levels (11%RH—33%–95%RH—11%RH) and ammonia (200–1200 ppm). The response and recovery times for the maximum response (under 11%RH–95%RH—11%RH and 1200ppm NH3) were 7 s and 26 s, respectively. The experimental observations confirmed that the resistance of the sensor depends on the concentration of H2O and NH3, both form the conjugate acid-base pair and which is responsible for the response of the sensor. Moreover, SnO2/SnO material as a catalyst possessed the good results for the degradation of MB (96%) and MO (84%) under visible light source. [ABSTRACT FROM AUTHOR]

We report the proof-of-concept of molecularly imprinted polymer (MIP) functionalized Bi2S3/Ti3C2TX MXene nanocomposites for photoelectrochemical (PEC)/electrochemical (EC) dual-mode sensing of chlorogenic acid (CGA). Specifically, the in-situ growth of the Bi2S3/Ti3C2TX MXene served as a transducer substrate for molecularly imprinted polymers such as PEC and EC signal generators, due to its high surface area, suitable bandwidth and abundant active sites. In addition, the chitosan as a binder was encapsulated into MIP by means of phase inversion on a fluorine-doped tin dioxide (FTO) electrode. In the determination of CGA as an analytical model, the dual-mode sensor based on MIP functionalized Bi2S3/Ti3C2TX MXene nanocomposites had good selectivity, excellent stability and acceptable reproducibility, which displayed a linear concentration range from 0.0282 μM to 2824 μM for the PEC signal and 0.1412 μM to 22.59 μM for the EC signal with a low detection limit of 2.4 nM and 43.1 nM, respectively. Importantly, two dual-response mode with different transduction mechanisms could mutually conform to dramatically raise the reliability and accuracy of detection compared to single-mode detection. This work is a breakthrough for the design of dual-mode sensors and will provide a reasonable basis for the construction of dual-mode sensor platforms. [ABSTRACT FROM AUTHOR]

In addition to initiating immune and inflammatory responses, these signals engage numerous transport proteins (including two pore domain K SP + sp (K2P) channels and Trpm5 channels), enhancing mucociliary clearance crucial to host defense mechanisms. Their model interweaves actions of the Na SP + sp /K SP + sp -ATPase, NHE1, the Na SP + sp -HCO SB 3 sb SP - sp cotransporter 1 (NBCn1), Na SP + sp -coupled glucose and amino acid transporters, the epithelial Na SP + sp channel (ENaC), and voltage-gated sodium channels (i.e. Na SB V sb 1.5). In biological membranes, channels and transporters underlie essential processes that both mediate and impact crucial communications between the intracellular and extracellular milieus. [Extracted from the article]

Abstract Reconsolidation has been considered a process in which a consolidated memory is turned into a labile stage. Within the reconsolidation window, the labile memory can be either erased or strengthened. Manipulating acid-sensing ion channels (ASICs) in the amygdala via carbon dioxide (CO2) inhalation enhances memory retrieval and its lability within the reconsolidation window. Moreover, pairing CO2 inhalation with retrieval bears the reactivation of the memory trace and enhances the synaptic exchange of the calcium-impermeable AMPA receptors to calcium-permeable AMPA receptors. Our patch-clamp data suggest that the exchange of the AMPA receptors depends on the ubiquitin-proteasome system (UPS), via protein degradation. Ziram (50 µM), a ubiquitination inhibitor, reduces the turnover of the AMPA receptors. CO2 inhalation with retrieval boosts the ubiquitination without altering the proteasome activity. Several calcium-dependent kinases potentially involved in the CO2-inhalation regulated memory liability were identified using the Kinome assay. These results suggest that the UPS plays a key role in regulating the turnover of AMPA receptors during CO2 inhalation.

Abstract Background Tumor necrosis factor-α (TNF-α) is a pro-inflammatory cytokine involved in pain processing and hypersensitivity. It regulates not only the expression of a variety of inflammatory mediators but also the functional activity of some ion channels. Acid-sensing ion channels (ASICs), as key sensors for extracellular protons, are expressed in nociceptive sensory neurons and contribute to pain signaling caused by tissue acidosis. It is still unclear whether TNF-α has an effect on functional activity of ASICs. Herein, we reported that a brief exposure of TNF-α acutely sensitized ASICs in rat dorsal root ganglion (DRG) neurons. Methods Electrophysiological experiments on rat DRG neurons were performed in vitro and acetic acid induced nociceptive behavior quantified in vitro. Results A brief (5min) application of TNF-α rapidly enhanced ASIC-mediated currents in rat DRG neurons. TNF-α (0.1-10 ng/ml) dose-dependently increased the proton-evoked ASIC currents with an EC50 value of 0.12 ± 0.01 nM. TNF-α shifted the concentration-response curve of proton upwards with a maximal current response increase of 42.34 ± 7.89%. In current-clamp recording, an acute application of TNF-α also significantly increased acid-evoked firing in rat DRG neurons. The rapid enhancement of ASIC-mediated electrophysiological activity by TNF-α was prevented by p38 mitogen-activated protein kinase (MAPK) inhibitor SB202190, but not by non-selective cyclooxygenase inhibitor indomethacin, suggesting that p38 MAPK is necessary for this enhancement. Behaviorally, TNF-α exacerbated acid-induced nociceptive behaviors in rats via activation of local p38 MAPK pathway. Conclusions These results suggest that TNF-α rapidly enhanced ASIC-mediated functional activity via a p38 MAPK pathway, which revealed a novel peripheral mechanism underlying TNF-α involvement in rapid hyperalgesia by sensitizing ASICs in primary sensory neurons.

A two-way relationship exists between type 2 diabetes (T2DM) and human nonalcoholic steatohepatitis (NASH). Several diabetic NASH models have the disadvantages of long cycles or inconsistent with the actual incidence of human disease, which would be costly and time-consuming to investigate disease pathogenesis and develop drugs. Therefore, there is an urgent need to establish a diabetic NASH mouse model. The combination between Fructose-palmitate-cholesterol diet (FPC) and Streptozotocin (STZ) (FPC+STZ) was used to construct diabetic NASH mouse model. The in vivo effects of silencing acid-sensitive Ion Channel 1a (ASIC1a) were examined with an adeno-associated virus 9 (AAV9) carrying ASIC1a short hairpin RNA (shRNA) in FPC+STZ model. The mice fed with FPC for 12 weeks had insulin resistance, hyperinsulinemia, lipid accumulation, and increased hepatic levels of inflammatory factors. However, it still did not develop remarkable liver fibrosis. Most interestingly, noticeable fibrotic scars were observed in the liver of mice from FPC+STZ group. Furthermore, insulin therapy significantly ameliorated FPC+STZ-induced NASH-related liver fibrosis, indicating that hyperglycemia is of great significance in NASH development and progression. Importantly, ASIC1a was found to be involved in the pathogenesis of diabetic NASH as demonstrated that silencing ASIC1a in HSCs significantly ameliorated FPC+STZ-induced NASH fibrosis. Mechanistically, ASIC1a interacted with Poly Adp-adenosine ribose polymerase (PARP1) to promote HSC activation by inducing autophagy. A FPC diet combined with an injection of STZ induces a diabetic NASH mouse model in a shorter period. Targeting ASIC1a may provide a novel therapeutic target for the treatment of diabetic NASH. [ABSTRACT FROM AUTHOR]

Acid-sensing ion channels (ASICs) have been known as sensors of a local pH change within both physiological and pathological conditions. ASIC-targeting peptide toxins could be potent molecular tools for ASIC-manipulating in vitro, and for pathology treatment in animal test studies. Two sea anemone toxins, native Hmg 1b-2 and recombinant Hmg 1b-4, both related to APETx-like peptides, inhibited the transient current component of human ASIC3-Δ20 expressed in Xenopus laevis oocytes, but only Hmg 1b-2 inhibited the rat ASIC3 transient current. The Hmg 1b-4 action on rASIC3 as a potentiator was confirmed once again. Both peptides are non-toxic molecules for rodents. In open field and elevated plus maze tests, Hmg 1b-2 had more of an excitatory effect and Hmg 1b-4 had more of an anxiolytic effect on mouse behavior. The analgesic activity of peptides was similar and comparable to diclofenac activity in an acid-induced muscle pain model. In models of acute local inflammation induced by λ-carrageenan or complete Freund’s adjuvant, Hmg 1b-4 had more pronounced and statistically significant anti-inflammatory effects than Hmg 1b-2. It exceeded the effect of diclofenac and, at a dose of 0.1 mg/kg, reduced the volume of the paw almost to the initial volume. Our data highlight the importance of a comprehensive study of novel ASIC-targeting ligands, and in particular, peptide toxins, and present the slightly different biological activity of the two similar toxins.

Activation of central respiratory chemoreceptors provides excitatory drive to both respiratory and sympathetic outputs. The enhanced respiratory-sympathetic coupling contributes to the onset and development of hypertension. However, the specific central targets and molecular mechanisms involved in this process remain elusive. This study aimed to investigate the role of acid-sensing ion channel 1 (ASIC1) in nucleus tractus solitarii (NTS) neurons in CO 2 -stimulated cardiorespiratory effects in spontaneously hypertensive rats (SHRs). Respiration and blood pressure of conscious rats were recorded by whole-body plethysmography and telemetry, respectively. Western blot was used to detect the expression difference of ASIC1 protein in NTS region between Wistar-Kyoto (WKY) rats and SHRs. Excitability of NTS neurons were assessed by extracellular recordings. Compared to WKY rats, the enhanced CO 2 -stimulated cardiopulmonary effect and up-regulation of ASIC1 in the NTS were already observed in 4-week-old prehypertensive SHRs. Furthermore, specific blockade of ASIC1 effectively attenuated the CO 2 -stimulated increase in firing rate of NTS neurons in anesthetized adult SHRs. Intracerebroventricular injections of the ASIC1a blocker PcTx1 or knockdown Asic1 in NTS neurons significantly reduced the heightened CO 2 -stimulated ventilatory response, and diminished the CO 2 -stimulated increase in arterial pressure and heart rate in adult SHRs. These findings showed that dysregulated ASIC1 signaling in the NTS contribute to the exaggerated CO 2 -stimulated cardiorespiratory effects observed in SHRs. [ABSTRACT FROM AUTHOR]

Activation of hepatic stellate cells (HSCs) is a key cause of liver fibrosis. However, the mechanisms leading to the activation of HSCs are not fully understood. In the pathological process, acid-sensing ion channel 1a (ASIC1a) is widely involved in the development of inflammatory diseases, suggesting that ASIC1a may play an important role in liver fibrosis. We found that in an acidic environment, ASIC1a leads to HSC-T6 cell activation. Meanwhile, exosomes produced by activated HSC-T6 cells (HSC-EXOs) can be reabsorbed by quiescent HSC-T6 cells to promote their activation. Exosomes mainly carry miRNAs involved in intercellular information exchange. We performed exosome miRNA whole transcriptome sequencing. The results indicated that the acidic environment could alter the miRNA expression profile in the exosomes of HSC-T6 cells. Further studies revealed that ASIC1a promotes the activation of HSCs by regulating miR-301a-3p targeting B-cell translocation gene 1 (BTG1). In conclusion, our study found that ASIC1a may affect HSC activation through the exosomal miR-301a-3p/BTG1 axis, and inhibiting ASIC1a may be a promising treatment strategy for liver fibrosis. [ABSTRACT FROM AUTHOR]

Lung cancer is one of the most common cancer types in the world. Despite existing treatment strategies, overall patient survival remains low and new targeted therapies are required. Acidification of the tumor microenvironment drives the growth and metastasis of many cancers. Acid sensors such as acid-sensing ion channels (ASICs) may become promising targets for lung cancer therapy. Previously, we showed that inhibition of the ASIC1 channels by a recombinant analogue of mambalgin-2 from Dendroaspis polylepis controls oncogenic processes in leukemia, glioma, and melanoma cells. Here, we studied the effects and molecular targets of mambalgin-2 in lung adenocarcinoma A549 and Lewis cells, lung transformed WI-38 fibroblasts, and lung normal HLF fibroblasts. We found that mambalgin-2 inhibits the growth and migration of A549, metastatic Lewis P29 cells, and WI-38 cells, but not of normal fibroblasts. A549, Lewis, and WI-38 cells expressed different ASIC and ENaC subunits, while normal fibroblasts did not at all. Mambalgin-2 induced G2/M cell cycle arrest and apoptosis in lung adenocarcinoma cells. In line, acidification-evoked inward currents were observed only in A549 and WI-38 cells. Gene knockdown showed that the anti-proliferative and anti-migratory activity of mambalgin-2 is dependent on the expression of ASIC1a, α-ENaC, and γ-ENaC. Using affinity extraction and immunoprecipitation, mambalgin-2 targeting of ASIC1a/α-ENaC/γ-ENaC heteromeric channels in A549 cells was shown. Electrophysiology studies in Xenopus oocytes revealed that mambalgin-2 inhibits the ASIC1a/α-ENaC/γ-ENaC channels with higher efficacy than the ASIC1a channels, pointing on the heteromeric channels as a primary target of the toxin in cancer cells. Finally, bioinformatics analysis showed that the increased expression of ASIC1 and γ-ENaC correlates with a worse survival prognosis for patients with lung adenocarcinoma. Thus, the ASIC1a/α-ENaC/γ-ENaC heterotrimer can be considered a marker of cell oncogenicity and its targeting is promising for the design of new selective cancer therapeutics. [ABSTRACT FROM AUTHOR]

Specific amino acid substitutions in degenerin mechano-gated channels (DEGs) of C. elegans convert these channels into constitutively active mutants that induce the degeneration of neurons where DEGs are expressed. Acid-sensing ion channel-2a (ASIC2a), a proton-gated cation channel predominantly expressed in central neurons, is a mammalian ortholog of DEGs, and it can remain unclosed to be cytotoxic once the same mutations as the DEG mutants are introduced into its gene. Here we show that heterozygous transgenic (Tg) rats expressing ASIC2a-G430F (ASIC2aG430F), the most active form of the gain-of-function mutants, under the control of the intrinsic ASIC2a promoter exhibited marked cerebellar maldevelopment with mild whole-brain atrophy. The Tg rats were small and developed an early-onset ataxic gait, as evidenced by rotarod and footprint tests. The overall gross-anatomy of the Tg brain was normal just after birth, but a reduction in brain volume, especially cerebellar volume, gradually emerged with age. Histological examination of the adult Tg brain revealed that the cell-densities of cerebellar Purkinje and granule cells were markedly reduced, while the cytoarchitecture of other brain regions was not significantly altered. RT-PCR and immunoblot analyses demonstrated that ASIC2aG430F transcripts and proteins were already present in various regions of the neonatal Tg brain before the deforming cerebellum became apparent. These results suggest that, according to the spatiotemporal pattern of the wild-type (WT) ASIC2a gene expression, the ASIC2aG430F channel induced lethal degeneration in Tg brain neurons expressing both ASIC2aG430F and ASIC2a channels. · Transgenic (Tg) rats carrying an ASIC2a gain-of-function mutation were produced. · The brain volume, especially cerebellar volume, of Tg rats significantly decreased. · Cerebellar Purkinje and granule cells markedly degenerated in Tg rats. · Rotarod tests revealed that Tg rats developed an early-onset ataxic gait. · This is the first description of an ASIC gain-of-function mutant mammal. [ABSTRACT FROM AUTHOR]

Lysophosphatidyl-choline (LPC), a member of the phospholipid family, is an emerging player in pain. It is known to modulate different pain-related ion channels, including Acid-Sensing Ion Channel 3 (ASIC3), a cationic channel mainly expressed in peripheral sensory neurons. LPC potentiates ASIC3 current evoked by mild acidifications, but can also activate the channel at physiological pH. Very recently, LPC has been associated to chronic pain in patients suffering from fibromyalgia or osteoarthritis. Accordingly, repetitive injections of LPC within mouse muscle or joint generate both persistent pain-like and anxiety-like behaviors in an ASIC3-dependent manner. LPC has also been reported to generate acute pain behaviors when injected intraplantarly in rodents. Here, we explore the mechanism of action of a single cutaneous injection of LPC by studying its effects on spinal dorsal horn neurons. We combine pharmacological, molecular and functional approaches including in vitro patch clamp recordings and in vivo recordings of spinal neuronal activity. We show that a single cutaneous injection of LPC exclusively affects the nociceptive pathway, inducing an ASIC3-dependent sensitization of nociceptive fibers that leads to hyperexcitabilities of both high threshold (HT) and wide dynamic range (WDR) spinal neurons. ASIC3 is involved in LPC-induced increase of WDR neuron's windup as well as in WDR and HT neuron's mechanical hypersensitivity, and it participates, together with TRPV1, to HT neuron's thermal hypersensitivity. The nociceptive input induced by a single LPC cutaneous rather induces short-term sensitization, contrary to previously described injections in muscle and joint. If the effects of peripheral LPC on nociceptive pathways appear to mainly depend on peripheral ASIC3 channels, their consequences on pain may also depend on the tissue injected. Our findings contribute to a better understanding of the nociceptive signaling pathway activated by peripheral LPC via ASIC3 channels, which is an important step regarding the ASIC3-dependent roles of this phospholipid in acute and chronic pain conditions. [ABSTRACT FROM AUTHOR]

The transient receptor potential vanilloid 1 (TRPV1) ion channel plays an important role in the peripheral nociceptive pathway. TRPV1 is a polymodal receptor that can be activated by multiple types of ligands and painful stimuli, such as noxious heat and protons, and contributes to various acute and chronic pain conditions. Therefore, TRPV1 is emerging as a novel therapeutic target for the treatment of various pain conditions. Notably, various peptides isolated from venomous animals potently and selectively control the activation and inhibition of TRPV1 by binding to its outer pore region. This review will focus on the mechanisms by which venom-derived peptides interact with this portion of TRPV1 to control receptor functions and how these mechanisms can drive the development of new types of analgesics. [ABSTRACT FROM AUTHOR]

Multidrug resistance is the main obstacle to curing hepatocellular carcinoma (HCC). Acid-sensing ion channel 1a (ASIC1a) has critical roles in all stages of cancer progression, especially invasion and metastasis, and in resistance to therapy. Epithelial to mesenchymal transition (EMT) transforms epithelial cells into mesenchymal cells after being stimulated by extracellular factors and is closely related to tumour infiltration and resistance. We used Western blotting, immunofluorescence, qRT-PCR, immunohistochemical staining, MTT, colony formation and scratch healing assay to determine ASIC1a levels and its relationship to cell proliferation, migration and invasion. ASIC1a is overexpressed in HCC tissues, and the amount increased in resistant HCC cells. EMT occurred more frequently in drug-resistant cells than in parental cells. Inactivation of ASIC1a inhibited cell migration and invasion and increased the chemosensitivity of cells through EMT. Overexpression of ASIC1a upregulated EMT and increased the cells’ proliferation, migration and invasion and induced drug resistance; knocking down ASIC1a with shRNA had the opposite effects. ASIC1a increased cell migration and invasion through EMT by regulating α and β-catenin, vimentin and fibronectin expression via the AKT/GSK-3β/Snail pathway driven by TGFβ/Smad signals. ASIC1a mediates drug resistance of HCC through EMT via the AKT/GSK-3β/ Snail pathway. [ABSTRACT FROM AUTHOR]

Soybean (Glycine max) is an important crop globally for food and edible oil production. Soybean plants are sensitive to salinity (NaCl), with significant yield decreases reported under saline conditions. GmSALT3 is the dominant gene underlying a major QTL for salt tolerance in soybean. GmSALT3 encodes a transmembrane protein belonging to the plant cation/proton exchanger (CHX) family, and is predominately expressed in root phloem and xylem associated cells under both saline and non‐saline conditions. It is currently unknown through which molecular mechanism(s) the ER‐localised GmSALT3 contributes to salinity tolerance, as its localisation excludes direct involvement in ion exclusion. In order to gain insights into potential molecular mechanism(s), we used RNA‐seq analysis of roots from two soybean NILs (near isogenic lines); NIL‐S (salt‐sensitive, Gmsalt3), and NIL‐T (salt‐tolerant, GmSALT3), grown under control and saline conditions (200 mM NaCl) at three time points (0 h, 6 h, and 3 days). Gene ontology (GO) analysis showed that NIL‐T has greater responses aligned to oxidation reduction. ROS were less abundant and scavenging enzyme activity was greater in NIL‐T, consistent with the RNA‐seq data. Further analysis indicated that genes related to calcium signalling, vesicle trafficking and Casparian strip (CS) development were upregulated in NIL‐T following salt treatment. We propose that GmSALT3 improves the ability of NIL‐T to cope with saline stress through preventing ROS overaccumulation in roots, and potentially modulating Ca2+ signalling, vesicle trafficking and formation of diffusion barriers. [ABSTRACT FROM AUTHOR]

Voltage‐gated proton channels (HV1) have been found in many mammalian cells and play a crucial role in the immune system, male fertility, and cancer progression. Glycosaminoglycans play a significant role in various aspects of cell physiology, including the modulation of membrane receptors and ion channel function. We present here evidence that mechanosensitivity of the dimeric HV1 channel transduce changes on cell membrane fluidity related to the defective biosynthesis of chondroitin sulfate and heparan sulfate in Chinese Hamster Ovary (CHO‐745) cells into a leftward shift in the activation voltage dependence. This effect was accompanied by an increase in the H+ current, and an acceleration of the activation kinetics, under symmetrical or asymmetrical pH gradient (ΔpH) conditions. Similar gating alterations were evoked by two naturally occurring HV1 N‐terminal truncated isoforms expressed in wild‐type CHO‐K1 and CHO‐745 cells. On three different monomeric HV1 constructs, no alterations in the biophysical parameters were observed. Moreover, we have shown that HV1 gating can be modulated by manipulating CHO‐K1 cell membrane fluidity. Our results suggest that the defective biosynthesis of chondroitin sulfate and heparan sulfate on CHO‐745 cell increases membrane fluidity and allosterically modulates the coupling between voltage‐ and ΔpH‐sensing through the dimeric HV1 channel. [ABSTRACT FROM AUTHOR]

The global dissemination of antibiotic resistance genes (ARGs), especially via plasmid-mediated horizontal transfer, is becoming a pervasive health threat. While our previous study found that herbicides can accelerate the horizontal gene transfer (HGT) of ARGs in soil bacteria, the underlying mechanisms by which herbicides promote the HGT of ARGs across and within bacterial genera are still unclear. Here, the underlying mechanism associated with herbicide-promoted HGT was analyzed by detecting intracellular reactive oxygen species (ROS) production, extracellular polymeric substance composition, cell membrane integrity and proton motive force combined with genome-wide RNA sequencing. Exposure to herbicides induced a series of the above bacterial responses to promote HGT except for the ROS response, including compact cell-to-cell contact by enhancing pilus-encoded gene expression and decreasing cell surface charge, increasing cell membrane permeability, and enhancing the proton motive force, providing additional power for DNA uptake. This study provides a mechanistic understanding of the risk of bacterial resistance spread promoted by herbicides, which elucidates a new perspective on nonantibiotic agrochemical acceleration of the HGT of ARGs. [Display omitted]. [ABSTRACT FROM AUTHOR]

In independent studies, our laboratory has shown the importance of the degenerin proteins β-epithelial Na+ channel (βENaC) and acid-sensing ion channel 2 (ASIC2) in pressure-induced constriction (PIC) in renal interlobar arteries. Most, but not all, of the PIC response is abolished in mice lacking normal levels of βENaC or in ASIC2-null mice, indicating that the functions of βENaC and ASIC2 cannot fully compensate for the loss of the other. Degenerin proteins are known to associate and form heteromeric channels in expression systems, but whether they interact biochemically and functionally in vascular smooth muscle cells is unknown. We hypothesized that βENaC and ASIC2 interact to mediate PIC responses in renal vessels. To address this possibility, we 1) used biochemical approaches to show that βENaC associates into high-molecular-weight complexes and immunoprecipitants with ASIC2 in vascular smooth muscle cells and then 2) examined PIC in renal afferent arterioles in mice lacking normal levels of βENaC (βENaCm/m) or/and ASIC2 (ASIC2-/-) using the isolated afferent arteriole-attached glomerulus preparation. We found that the sensitivity of the PIC response (slope of the relationship between intraluminal pressure and percent myogenic tone) decreased to 26%, 27%, and -8% of wild-type controls in ASIC2-/-, βENaCm/m, and ASIC2-/-/βENaCm/m groups, respectively, suggesting that the PIC response was totally abolished in mice deficient in both ASIC2 and βENaC. Surprisingly, we found that resting internal diameters were 20-30% lower (60 mmHg, Ca2+ free) in ASIC2-/-/βENaCm/m (11.3 ± 0.5 µm) mice compared with control (14.4 ± 0.6 µm, P = 0.0007, independent two-tailed t test) or singly modified (15.7 ± 1.0 to 16.3 ± 1.1 µm) mice, suggesting compensatory vasoconstriction or remodeling. We then examined mean arterial blood pressure (MAP) using radiotelemetry and glomerular injury using histological examination of renal sections. We found that 24-h MAP was mildly elevated ( + 8 mmHg) in ASIC2-/-/βENaCm/m mice versus wild-type controls and the glomerular injury score was modestly increased by 38%. These findings demonstrate that myogenic constriction in afferent arterioles is dependent on normal expression of βENaC and ASIC2 and that mice lacking normal levels of ASIC2 and βENaC have mild renal injury and increased MAP. [ABSTRACT FROM AUTHOR]

Mechanical and metabolic signals associated with skeletal muscle contraction stimulate the sensory endings of thin fibre muscle afferents, which, in turn, generates reflex increases in sympathetic nerve activity (SNA) and blood pressure (the exercise pressor reflex; EPR). EPR activation in patients and animals with heart failure with reduced ejection fraction (HF‐rEF) results in exaggerated increases in SNA and promotes exercise intolerance. In the healthy decerebrate rat, a subtype of acid sensing ion channel (ASIC) on the sensory endings of thin fibre muscle afferents, namely ASIC1a, has been shown to contribute to the metabolically sensitive portion of the EPR (i.e. metaboreflex), but not the mechanically sensitive portion of the EPR (i.e. the mechanoreflex). However, the role played by ASIC1a in evoking the EPR in HF‐rEF is unknown. We hypothesized that, in decerebrate, unanaesthetized HF‐rEF rats, injection of the ASIC1a antagonist psalmotoxin‐1 (PcTx‐1; 100 ng) into the hindlimb arterial supply would reduce the reflex increase in renal SNA (RSNA) evoked via 30 s of electrically induced static hindlimb muscle contraction, but not static hindlimb muscle stretch (model of mechanoreflex activation isolated from contraction‐induced metabolite‐production). We found that PcTx‐1 reduced the reflex increase in RSNA evoked in response to muscle contraction (n = 8; mean (SD) ∫ΔRSNA pre: 1343 (588) a.u.; post: 816 (573) a.u.; P = 0.026) and muscle stretch (n = 6; ∫ΔRSNA pre: 688 (583) a.u.; post: 304 (370) a.u.; P = 0.025). Our data suggest that, in HF‐rEF rats, ASIC1a contributes to activation of the exercise pressor reflex and that contribution includes a novel role for ASIC1a in mechanosensation that is not present in healthy rats. Key points: Skeletal muscle contraction results in exaggerated reflex increases in sympathetic nerve activity in heart failure patients compared to healthy counterparts, which likely contributes to increased cardiovascular risk and impaired tolerance for even mild exercise (i.e. activities of daily living) for patients suffering with this condition.Activation of acid sensing ion channel subtype 1a (ASIC1a) on the sensory endings of thin fibre muscle afferents during skeletal muscle contraction contributes to reflex increases in sympathetic nerve activity and blood pressure, at least in healthy subjects.In this study, we demonstrate that ASIC1a on the sensory endings of thin fibre muscle afferents plays a role in both the mechanical and metabolic components of the exercise pressor reflex in male rats with heart failure.The present data identify a novel role for ASIC1a in evoking the exercise pressor reflex in heart failure and may have important clinical implications for heart failure patients. [ABSTRACT FROM AUTHOR]

The human palmar aponeurosis is involved in hand proprioception, and it contains different sensory corpuscle morphotypes that serve this role. In palmar fibromatosis (classically referred to as Dupuytren's disease), the palmar aponeurosis undergoes fibrous structural changes that, presumably, also affect the nervous system, causing altered perception. We analysed the various sensory nerve formation morphotypes in the palmar aponeuroses of healthy subjects and patients with palmar fibromatosis. To do this, we used immunohistochemistry for corpuscular constituents and the putative mechanoproteins PIEZO2 and acid‐sensing ion channel 2. Free nerve endings and Golgi‐Mazzoni, Ruffini, paciniform and Pacinian corpuscles were identified in both the healthy and the pathological conditions. The densities of the free nerve endings and Golgi‐Mazzoni corpuscles were slightly increased in the pathological tissues. Furthermore, the Pacinian corpuscles were enlarged and displayed an altered shape. Finally, there was also morphological and immunohistochemical evidence of occasional denervation of the Pacinian corpuscles, although no increase in their number was observed. Both PIEZO2 and acid‐sensing ion channel 2 were absent from the altered corpuscles. These results indicate that the human palmar aponeurosis is richly innervated, and the free nerve endings and sensory corpuscles within the palmar aponeurosis undergo quantitative and qualitative changes in patients with palmar fibromatosis, which may explain the sensory alterations occasionally reported for this pathology. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate the possible involvement of transient receptor potential (TRP) channels, Acid-sensing ion channels (ASIC) and N-Methyl-D-aspartate receptor (NMDAR) in the orofacial antinociceptive behaviour effect of botulinum toxin type A (BoNT/A) in adult zebrafish. Initially, the open field test was performed to evaluate the effect of BoNT/A on the locomotor activity of zebrafish. Subsequently, the animals were pretreated with BoNT/A (0.05U, 0.1U or 0.5U/masseter) and acute orofacial nociception was induced by cinnamaldehyde, capsaicin, menthol, acid saline or glutamate applied to the lip or masseter muscle. In another group of experiments, animals were pre-treated with capsazepine (TRPV1 antagonist) or ketamine (NMDAR antagonist) to investigate the mechanism of antinociception. The possible involvement of central C-fibre afferents was also investigated using capsaicin desensitized animals. A molecular docking study was performed to observe the in silico interaction of BoNT/A with TRPV1 and NMDA channels. Pretreatment with BoNT/A reduced the nociceptive behaviour induced by capsaicin and glutamate. Antinociception was effectively inhibited by capsazepine and ketamine, as well as by capsaicin-induced desensitization. Consistent with these in vivo findings, the molecular docking study indicated that BoNT/A can interact with TRPV1 and NMDAR. The results indicate the involvement of TRP and NMDAR mechanisms in the orofacial antinociceptive behaviour effect of BoNT/A. The results also confirm the pharmacological relevance of BoNT/A as an inhibitor of orofacial nociception behaviour. • The use of BoNT/A can inhibit orofacial nociceptive behaviour in adult zebrafish. • BoNT/A-related pain control may involve modulation of NMDA and TRPV1 receptors. • Molecular docking indicated that BoNT/A can interact with TRPV1 and NMDAR. • BoNT/A can reduce the nociceptive effect of sensitized TRPV1 receptors. [ABSTRACT FROM AUTHOR]

• Acidification is induced in the gingival sulcus of mechanically forced tooth. • Buffering the gingival acidity ameliorates orthodontic mechanical allodynia. • ASIC3 is involved in the mechanical allodynia induced by orthodontic force. • Tooth movement causes ASIC3 phosphorylation in the periodontal tissue. Tooth movements associated with orthodontic treatment often cause tooth pain. However, the detailed mechanism remains unclear. Here, we examined the involvement of periodontal acidification caused by tooth movement in mechanical tooth pain hypersensitivity. Elastics were inserted between the first and second molars to move the teeth in Sprague-Dawley rats. Mechanical head-withdrawal reflex threshold to first molar stimulation and the pH of the gingival sulcus around the tooth were measured. The expression of acid-sensing ion channel 3 (ASIC3) in trigeminal ganglion neurons and phosphorylation of ASIC3 in the periodontal tissue were analyzed. The mechanical head-withdrawal reflex threshold to first molar stimulation and pH in the gingival sulcus decreased on day 1 after the elastic insertion. These decreases recovered to the sham level by buffering periodontal acidification. Periodontal inhibition of ASIC3 channel activity reversed the decreased mechanical head-withdrawal reflex threshold to first molar stimulation. On day 1 after elastic insertion, the tooth movement did not change the number of ASIC3 immunoreactive trigeminal ganglion neurons innervating the periodontal tissue but increased phosphorylated-ASIC3 levels in the periodontal tissue. Periodontal acidification induced by tooth movement causes phosphorylation of ASIC3, resulting in mechanical pain hypersensitivity in mechanically forced tooth. [ABSTRACT FROM AUTHOR]

Acid‐sensing ion channels (ASICs) participate in synaptic transmission due to the acidic content of synaptic vesicles, but their contribution to postsynaptic currents is small. This has stimulated attempts to find endogenous ASIC potentiators that could enhance ASIC‐mediated currents to physiologically relevant values. Here we demonstrate that glutamate, which serves as a neurotransmitter, potentiates recombinant ASIC1a in the submillimolar concentration range. The effect of glutamate is especially interesting as ASIC's presence has been shown in glutamatergic synapses. At pH=6.5 glutamate had maximum potentiation of 87% with an EC50 value of 0.65 mM. The mechanism of potentiation is due to a shift of pH‐dependent activation to less acidic values, with 0.5 mM glutamate increasing pH50 from 6.04 to 6.43. Due to this mechanism, ASIC1a in glutamatergic synapses might be intrinsically potentiated. Furthermore, this effect could compensate for the inhibition of ionotropic glutamate receptors by extracellular acidification during synaptic transmission. [ABSTRACT FROM AUTHOR]

In proton exchange membrane fuel cells (PEMFCs), the avoidance and detection of failures such as flooding and dry‐out are crucial. Non‐destructive measurement approaches using magnetic sensors have been developed for this purpose. To reduce the number of sensors required to be installed in a PEMFC system for evaluation, we propose a control method for PEMFCs using the magnetic flux density as an index. The proposed method determines the failure conditions by calculating a simple current mapping with a reduced number of sensors. The results of four‐point magnetic flux densities under failure conditions and stable control using two‐point measurement indices are presented. [ABSTRACT FROM AUTHOR]

Similar to most large toxins, the chemical synthesis of -bungarotoxin is challenging, explaining why all previous reports use purified or recombinant -bungarotoxin. , gave rise to three thematic sessions: the first on plant toxins, algal toxins and mycotoxins; the second on animal toxins; and the third on bacterial toxins. -Bungarotoxin is a large, 74 amino acid toxin containing five disulfide bridges, initially identified in the venom of I Bungarus multicinctus i snake. Gambierol is a polycyclic ether toxin produced by the dinoflagellate I Gambierdiscus toxicus i that is a potent neurotoxin by blocking voltage-gated potassium channels. [Extracted from the article]

The loss of skeletal muscle function with age, known as sarcopenia, significantly reduces independence and quality of life and can have significant metabolic consequences. Although exercise is effective in treating sarcopenia it is not always a viable option clinically, and currently, there are no pharmacological therapeutic interventions for sarcopenia. Here, we show that chronic treatment with pan-adiponectin receptor agonist AdipoRon improved muscle function in male mice by a mechanism linked to skeletal muscle metabolism and tissue remodeling. In aged mice, 6 weeks of AdipoRon treatment improved skeletal muscle functional measures in vivo and ex vivo. Improvements were linked to changes in fiber type, including an enrichment of oxidative fibers, and an increase in mitochondrial activity. In young mice, 6 weeks of AdipoRon treatment improved contractile force and activated the energy-sensing kinase AMPK and the mitochondrial regulator PGC-1a (peroxisome proliferator-activated receptor gamma coactivator one alpha). In cultured cells, the AdipoRon induced stimulation of AMPK and PGC-1a was associated with increased mitochondrial membrane potential, reorganization of mitochondrial architecture, increased respiration, and increased ATP production. Furthermore, the ability of AdipoRon to stimulate AMPK and PGC1a was conserved in nonhuman primate cultured cells. These data show that AdipoRon is an effective agent for the prevention of sarcopenia in mice and indicate that its effects translate to primates, suggesting it may also be a suitable therapeutic for sarcopenia in clinical application. [ABSTRACT FROM AUTHOR]

Acidosis is a hallmark of ischemic stroke and a promising neuroprotective target for preventing neuronal injury. Previously, genetic manipulations showed that blockade of acid-sensing ion channel 1a (ASIC1a)-mediated acidotoxicity could dramatically alleviate the volume of brain infarct and restore neurological function after cerebral ischemia. However, few pharmacological candidates have been identified to exhibit efficacy on ischemic stroke through inhibition of ASIC1a. In this work, we examined the ability of a toxin-inspired compound 5b (C5b), previously found to effectively inhibit ASIC1a in vitro , to exert protective effects in animal models of ischemic stroke in vivo. We found that C5b exerts significant neuroprotective effects not only in acid-induced neuronal death in vitro but also ischemic brain injury in vivo , suggesting that ASIC1a is a druggable target for therapeutic development. More importantly, C5b is able to cross the blood brain barrier and significantly reduce brain infarct volume when administered intravenously in the ischemic animal model, highlighting its systemic availability for therapies against neurodegeneration due to acidotoxicity. Together, our data demonstrate that C5b is a promising lead compound for neuroprotection through inhibiting ASIC1a, which warrants further translational studies. [ABSTRACT FROM AUTHOR]

Introduction: Chronic cough heavily affects patients' quality of life, and there are no effective licensed therapies available. Cough is a complication of severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) infection, asthma, and other diseases. Patients with various diseases have a different profile of tussive responses to diverse cough triggers, thereby suggesting sundry mechanisms of neuronal dysfunctions. Previously, we demonstrated that the small molecule drug XC8 shows a clinical anti-asthmatic effect. The objective of the present study was to investigate the effect of XC8 on cough. Methods: We studied the antitussive effect of XC8 on cough induced by agonists activating human transient receptor potential (TRP) cation channels TRPA1 or TRPV1 in guinea pigs. We checked the agonistic/antagonistic activity of XC8 on the human cation channels TRPA1, TRPV1, TRPM8, P2X purinoceptor 2 (P2X2), and human acid sensing ion channel 3 (hASIC3) in Fluorescent Imaging Plate Reader (FLIPR) assay. Results: XC8 demonstrated clear antitussive activity and dose-dependently inhibited cough in guinea pigs induced by citric acid alone (up to 67.1%) or in combination with IFN-γ (up to 76.4%). XC8 suppressed cough reflexes induced by the repeated inhalation of citric acid (up to 80%) or by cinnamaldehyde (up to 60%). No activity of XC8 against cough evoked by capsaicin was revealed. No direct agonistic/antagonistic activity of XC8 on human TRPA1, TRPV1, TRPM8, P2X2, or hASIC3 was detected. Conclusions: XC8 acts against cough evoked by the activation of TRPA1 (citric acid/cinnamaldehyde) but not TRPV1 (capsaicin) channels. XC8 inhibits the cough reflex and suppresses the cough potentiation by IFN-γ. XC8 might be of significant therapeutic value for patients suffering from chronic cough associated with inflammation. [ABSTRACT FROM AUTHOR]

Acid-sensitive ion channel 1a (ASIC1a), which is abundant in chondrocytes, can sense changes in extracellular acidification. Our previous data demonstrated that ASIC1a is involved in acid-induced rat articular chondrocyte damage in osteoarthritis; however, its specific mechanisms remain unclear. The present study aims to explore the role of ASIC1a in rat articular chondrocyte senescence. RNA-seq transcriptome analysis identified senescence-associated secretory phenotype and matrix metalloproteinases genes were overexpressed by extracellular acidification (pH 6.0) in rat articular chondrocytes. An increase in senescence-associated β-galactosidase and senescence-related markers p16, p21 and p53 was observed in the pH 6.0-treated group compared with the control group. Acid-induced senescence-related markers could be blocked by the ASIC1a-specific inhibitor psalmotoxin-1 in rat articular chondrocytes and human immortalized C28/I2 chondrocyte cell lines. Moreover, our results showed that extracellular acidification increased autophagosomes and the autophagy-related proteins LC3B-II and Beclin-1; these effects could also be reversed by psalmotoxin-1 treatment, indicating ASIC1a participated in acid-induced chondrocyte autophagy. Blocking ASIC1a-mediated autophagy with chloroquine also inhibited senescence-related markers, decreased ROS expression, and restored cell membrane potential induced by pH 6.0 treatment. Taken together, these findings suggested that ASIC1a may be involved in acid-induced rat articular chondrocyte senescence by activating autophagy, which provides a potential therapeutic strategy for the treatment of osteoarthritis. [ABSTRACT FROM AUTHOR]

Acid-sensing ion channels (ASICs) are trimeric proton-gated cation channels involved in fast synaptic transmission. Pharmacological inhibition of ASIC1a reduces neurotoxicity and stroke infarct volumes, with the cysteine knot toxin psalmotoxin-1 (PcTx1) being one of the most potent and selective inhibitors. PcTx1 binds at the subunit interface in the extracellular domain (ECD), but the mechanism and conformational consequences of the interaction, as well as the number of toxin molecules required for inhibition, remain unknown. Here, we use voltage-clamp fluorometry and subunit concatenation to decipher the mechanism and stoichiometry of PcTx1 inhibition of ASIC1a. Besides the known inhibitory binding mode, we propose PcTx1 to have at least two additional binding modes that are decoupled from the pore. One of these modes induces a long-lived ECD conformation that reduces the activity of an endogenous neuropeptide. This long-lived conformational state is proton-dependent and can be destabilized by a mutation that decreases PcTx1 sensitivity. Lastly, the use of concatemeric channel constructs reveals that disruption of a single PcTx1 binding site is sufficient to destabilize the toxin-induced conformation, while functional inhibition is not impaired until two or more binding sites are mutated. Together, our work provides insight into the mechanism of PcTx1 inhibition of ASICs and uncovers a prolonged conformational change with possible pharmacological implications. [ABSTRACT FROM AUTHOR]

Background: Ineffective esophageal motility (IEM) is the most common motility disorder. However, little is known about its pathophysiology. Vagal afferent nerves convey esophageal intraluminal bolus information to solitary nucleus, which is likely to be involved with esophageal primary and secondary peristalsis (SP). We hypothesized that altered mucosal sensory afferents underlie the pathogenesis of IEM. Methods: We prospectively collected esophageal biopsies from 38 patients with proton pump inhibitor‐refractory reflux symptoms from January to December 2019. All patients underwent high‐resolution manometry for the evaluation of primary and secondary peristalsis, and off‐PPI 24‐h impedance‐pH studies. Biopsies were analyzed using immunohistochemistry for identification of calcitonin gene‐related peptide‐immunoreactive (CGRP‐IR) nerves and qPCR for mRNA expression of potential mechanoreceptors. Key Results: Overall 32 patients were finally analyzed which consisted of 11 patients with normal motility and 21 patients with IEM. The position of mucosal CGRP‐IR nerves from the esophageal lumen did not differ between the two groups (the proximal esophagus (p = 0.52), the mid‐esophagus (p = 0.92), the distal esophagus (p = 0.29)) with the similar reflux profile. No difference was seen in the position of CGRP‐IR nerves between patients with successful triggering of SP and those unable to trigger SP. There was also no difference in mRNA expression of each potential mechanoreceptors (TRPA1, TRPV1, TRPV4, ASIC1, ASIC3) between the two groups. Conclusions and Inferences: Our study showed that mucosal sensory afferents nerve position and mRNA expression of potential mechanoreceptors did not correlate to weak esophageal contraction. [ABSTRACT FROM AUTHOR]

Background: Prostatitis is the third most common urologic condition affecting more than half the male population at some point in their lives. There are different categories of prostatitis, of which approximately 90% of cases can be classified under the National Institute of Health (NIH) type III category (chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS)) with no causative agents identified. CP/CPPS is associated with several symptoms, of which the most prominent being chronic pain. Despite its high incidence, pain management in patients with CP/CPPS has been poor, possibly due to the lack of understanding of aetiological factors and mechanisms underlying pain development. Methods: An extensive literature search of published articles on the molecular mechanisms of pain in CP/CPPS was conducted using PubMed and Google Scholar search engines (https://pubmed.ncbi.nlm.nih.gov and https://scholar.google.com). The terms used for the search were: prostatitis, pain mechanism in CP/CPPS, prostatitis pain models, acid-sensing ion channels (ASICs), transient receptor potential vanilloid type 1 (TRPVs), purinergic channels (P2X) in prostatitis pain mechanism and inflammatory mediators in CP/CPPS. The papers were identified based on the title and abstract, and after excluding the articles that did not emphasize the pain mechanism in CP/CPPS. Ninety-five articles (36 review and 59 original research papers) met our criteria and were included in the review. Results: A number of inflammatory mediator molecules and pain channels, including ASICs, transient receptor potential vanilloid channels (TRPVs) and P2Xs have been investigated for their role in prostatitis pain pathology using various animal models. Conclusion: This review summarizes the pain mechanisms in CP/CPPS focusing on the inflammatory mediators, neurotransmitters, pain-transducing ion channels and small animal models developed for studying prostatitis. [ABSTRACT FROM AUTHOR]

Background: Extracellular acidification is a common feature of atherosclerotic lesions, and such an acidic microenvironment impedes ATP-binding cassette transporter A1 (ABCA1)-mediated cholesterol efflux and promotes atherogenesis. However, the underlying mechanism is still unclear. Acid-sensing ion channel 1 (ASIC1) is a critical H+ receptor, which is responsible for the perception and transduction of extracellular acidification signals. Aim: In this study, we explored whether or how ASIC1 influences extracellular acidification-induced ABCA1-mediated cholesterol efflux from macrophage-derived foam cells. Methods: RAW 264.7 macrophages were cultured in an acidic medium (pH 6.5) to generate foam cells. Then the intracellular lipid deposition, cholesterol efflux, and ASIC1/calpain1/ABCA1 expressions were evaluated. Results: We showed that extracellular acidification enhanced ASIC1 expression and translocation, promoted calpain1 expression and lipid accumulation, and decreased ABCA1 protein expression as well as ABCA1-mediated cholesterol efflux. Of note, inhibiting ASIC1 activation with amiloride or Psalmotoxin 1 (PcTx-1) not only lowered calpain1 protein level and lipid accumulation but also enhanced ABCA1 protein levels and ABCA1-mediated cholesterol efflux of macrophages under extracellular acidification conditions. Furthermore, similar results were observed in macrophages treated with calpain1 inhibitor PD150606. Conclusion: Extracellular acidification declines cholesterol efflux via activating ASIC1 to promote calpain1-mediated ABCA1 degradation. Thus, ASIC1 may be a novel therapeutic target for atherosclerosis. [ABSTRACT FROM AUTHOR]